/*

StackBlur - a fast almost Gaussian Blur For Canvas

Version: 	0.5
Author:		Mario Klingemann
Contact: 	mario@quasimondo.com
Website:	http://www.quasimondo.com/StackBlurForCanvas
Twitter:	@quasimondo

In case you find this class useful - especially in commercial projects -
I am not totally unhappy for a small donation to my PayPal account
mario@quasimondo.de

Or support me on flattr:
https://flattr.com/thing/72791/StackBlur-a-fast-almost-Gaussian-Blur-Effect-for-CanvasJavascript

Copyright (c) 2010 Mario Klingemann

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.
*/

var mul_table = [
  512,
  512,
  456,
  512,
  328,
  456,
  335,
  512,
  405,
  328,
  271,
  456,
  388,
  335,
  292,
  512,
  454,
  405,
  364,
  328,
  298,
  271,
  496,
  456,
  420,
  388,
  360,
  335,
  312,
  292,
  273,
  512,
  482,
  454,
  428,
  405,
  383,
  364,
  345,
  328,
  312,
  298,
  284,
  271,
  259,
  496,
  475,
  456,
  437,
  420,
  404,
  388,
  374,
  360,
  347,
  335,
  323,
  312,
  302,
  292,
  282,
  273,
  265,
  512,
  497,
  482,
  468,
  454,
  441,
  428,
  417,
  405,
  394,
  383,
  373,
  364,
  354,
  345,
  337,
  328,
  320,
  312,
  305,
  298,
  291,
  284,
  278,
  271,
  265,
  259,
  507,
  496,
  485,
  475,
  465,
  456,
  446,
  437,
  428,
  420,
  412,
  404,
  396,
  388,
  381,
  374,
  367,
  360,
  354,
  347,
  341,
  335,
  329,
  323,
  318,
  312,
  307,
  302,
  297,
  292,
  287,
  282,
  278,
  273,
  269,
  265,
  261,
  512,
  505,
  497,
  489,
  482,
  475,
  468,
  461,
  454,
  447,
  441,
  435,
  428,
  422,
  417,
  411,
  405,
  399,
  394,
  389,
  383,
  378,
  373,
  368,
  364,
  359,
  354,
  350,
  345,
  341,
  337,
  332,
  328,
  324,
  320,
  316,
  312,
  309,
  305,
  301,
  298,
  294,
  291,
  287,
  284,
  281,
  278,
  274,
  271,
  268,
  265,
  262,
  259,
  257,
  507,
  501,
  496,
  491,
  485,
  480,
  475,
  470,
  465,
  460,
  456,
  451,
  446,
  442,
  437,
  433,
  428,
  424,
  420,
  416,
  412,
  408,
  404,
  400,
  396,
  392,
  388,
  385,
  381,
  377,
  374,
  370,
  367,
  363,
  360,
  357,
  354,
  350,
  347,
  344,
  341,
  338,
  335,
  332,
  329,
  326,
  323,
  320,
  318,
  315,
  312,
  310,
  307,
  304,
  302,
  299,
  297,
  294,
  292,
  289,
  287,
  285,
  282,
  280,
  278,
  275,
  273,
  271,
  269,
  267,
  265,
  263,
  261,
  259
]

var shg_table = [
  9,
  11,
  12,
  13,
  13,
  14,
  14,
  15,
  15,
  15,
  15,
  16,
  16,
  16,
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  17,
  17,
  17,
  17,
  17,
  17,
  17,
  18,
  18,
  18,
  18,
  18,
  18,
  18,
  18,
  18,
  19,
  19,
  19,
  19,
  19,
  19,
  19,
  19,
  19,
  19,
  19,
  19,
  19,
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  20,
  20,
  20,
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  20,
  20,
  20,
  20,
  20,
  21,
  21,
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  21,
  21,
  21,
  21,
  21,
  21,
  21,
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  21,
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  21,
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  21,
  21,
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  22,
  22,
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  23,
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  23,
  23,
  23,
  23,
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  23,
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  23,
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  24,
  24,
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  24,
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  24,
  24,
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  24,
  24,
  24,
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  24,
  24,
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  24,
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  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24,
  24
]

function premultiplyAlpha (imageData) {
  var pixels = imageData.data
  var size = imageData.width * imageData.height * 4

  for (var i = 0; i < size; i += 4) {
    var a = pixels[i + 3] / 255
    pixels[i] *= a
    pixels[i + 1] *= a
    pixels[i + 2] *= a
  }
}

function unpremultiplyAlpha (imageData) {
  var pixels = imageData.data
  var size = imageData.width * imageData.height * 4

  for (var i = 0; i < size; i += 4) {
    var a = pixels[i + 3]
    if (a != 0) {
      a = 255 / a
      pixels[i] *= a
      pixels[i + 1] *= a
      pixels[i + 2] *= a
    }
  }
}

function stackBlurImage (imageID, canvasID, radius, blurAlphaChannel) {
  var img = document.getElementById(imageID)
  var w = img.naturalWidth
  var h = img.naturalHeight

  var canvas = document.getElementById(canvasID)

  canvas.style.width = w + 'px'
  canvas.style.height = h + 'px'
  canvas.width = w
  canvas.height = h

  var context = canvas.getContext('2d')
  context.clearRect(0, 0, w, h)
  context.drawImage(img, 0, 0)

  if (isNaN(radius) || radius < 1) return

  if (blurAlphaChannel) {
    stackBlurCanvasRGBA(canvasID, 0, 0, w, h, radius)
  } else {
    stackBlurCanvasRGB(canvasID, 0, 0, w, h, radius)
  }
}

function stackBlurCanvasRGBA (id, top_x, top_y, width, height, radius) {
  if (isNaN(radius) || radius < 1) return
  radius |= 0

  var canvas = document.getElementById(id)
  var context = canvas.getContext('2d')
  var imageData

  try {
    try {
      imageData = context.getImageData(top_x, top_y, width, height)
    } catch (e) {
      // NOTE: this part is supposedly only needed if you want to work with local files
      // so it might be okay to remove the whole try/catch block and just use
      // imageData = context.getImageData( top_x, top_y, width, height );
      try {
        netscape.security.PrivilegeManager.enablePrivilege(
          'UniversalBrowserRead'
        )
        imageData = context.getImageData(top_x, top_y, width, height)
      } catch (e) {
        alert('Cannot access local image')
        throw new Error('unable to access local image data: ' + e)
      }
    }
  } catch (e) {
    alert('Cannot access image')
    throw new Error('unable to access image data: ' + e)
  }

  premultiplyAlpha(imageData)

  var pixels = imageData.data

  var x,
    y,
    i,
    p,
    yp,
    yi,
    yw,
    r_sum,
    g_sum,
    b_sum,
    a_sum,
    r_out_sum,
    g_out_sum,
    b_out_sum,
    a_out_sum,
    r_in_sum,
    g_in_sum,
    b_in_sum,
    a_in_sum,
    pr,
    pg,
    pb,
    pa,
    rbs

  var div = radius + radius + 1
  var w4 = width << 2
  var widthMinus1 = width - 1
  var heightMinus1 = height - 1
  var radiusPlus1 = radius + 1
  var sumFactor = radiusPlus1 * (radiusPlus1 + 1) / 2

  var stackStart = new BlurStack()
  var stack = stackStart
  for (i = 1; i < div; i++) {
    stack = stack.next = new BlurStack()
    if (i == radiusPlus1) var stackEnd = stack
  }
  stack.next = stackStart
  var stackIn = null
  var stackOut = null

  yw = yi = 0

  var mul_sum = mul_table[radius]
  var shg_sum = shg_table[radius]

  for (y = 0; y < height; y++) {
    r_in_sum = g_in_sum = b_in_sum = a_in_sum = r_sum = g_sum = b_sum = a_sum = 0

    r_out_sum = radiusPlus1 * (pr = pixels[yi])
    g_out_sum = radiusPlus1 * (pg = pixels[yi + 1])
    b_out_sum = radiusPlus1 * (pb = pixels[yi + 2])
    a_out_sum = radiusPlus1 * (pa = pixels[yi + 3])

    r_sum += sumFactor * pr
    g_sum += sumFactor * pg
    b_sum += sumFactor * pb
    a_sum += sumFactor * pa

    stack = stackStart

    for (i = 0; i < radiusPlus1; i++) {
      stack.r = pr
      stack.g = pg
      stack.b = pb
      stack.a = pa
      stack = stack.next
    }

    for (i = 1; i < radiusPlus1; i++) {
      p = yi + ((widthMinus1 < i ? widthMinus1 : i) << 2)
      r_sum += (stack.r = pr = pixels[p]) * (rbs = radiusPlus1 - i)
      g_sum += (stack.g = pg = pixels[p + 1]) * rbs
      b_sum += (stack.b = pb = pixels[p + 2]) * rbs
      a_sum += (stack.a = pa = pixels[p + 3]) * rbs

      r_in_sum += pr
      g_in_sum += pg
      b_in_sum += pb
      a_in_sum += pa

      stack = stack.next
    }

    stackIn = stackStart
    stackOut = stackEnd
    for (x = 0; x < width; x++) {
      pixels[yi] = (r_sum * mul_sum) >> shg_sum
      pixels[yi + 1] = (g_sum * mul_sum) >> shg_sum
      pixels[yi + 2] = (b_sum * mul_sum) >> shg_sum
      pixels[yi + 3] = (a_sum * mul_sum) >> shg_sum

      r_sum -= r_out_sum
      g_sum -= g_out_sum
      b_sum -= b_out_sum
      a_sum -= a_out_sum

      r_out_sum -= stackIn.r
      g_out_sum -= stackIn.g
      b_out_sum -= stackIn.b
      a_out_sum -= stackIn.a

      p = (yw + ((p = x + radius + 1) < widthMinus1 ? p : widthMinus1)) << 2

      r_in_sum += stackIn.r = pixels[p]
      g_in_sum += stackIn.g = pixels[p + 1]
      b_in_sum += stackIn.b = pixels[p + 2]
      a_in_sum += stackIn.a = pixels[p + 3]

      r_sum += r_in_sum
      g_sum += g_in_sum
      b_sum += b_in_sum
      a_sum += a_in_sum

      stackIn = stackIn.next

      r_out_sum += pr = stackOut.r
      g_out_sum += pg = stackOut.g
      b_out_sum += pb = stackOut.b
      a_out_sum += pa = stackOut.a

      r_in_sum -= pr
      g_in_sum -= pg
      b_in_sum -= pb
      a_in_sum -= pa

      stackOut = stackOut.next

      yi += 4
    }
    yw += width
  }

  for (x = 0; x < width; x++) {
    g_in_sum = b_in_sum = a_in_sum = r_in_sum = g_sum = b_sum = a_sum = r_sum = 0

    yi = x << 2
    r_out_sum = radiusPlus1 * (pr = pixels[yi])
    g_out_sum = radiusPlus1 * (pg = pixels[yi + 1])
    b_out_sum = radiusPlus1 * (pb = pixels[yi + 2])
    a_out_sum = radiusPlus1 * (pa = pixels[yi + 3])

    r_sum += sumFactor * pr
    g_sum += sumFactor * pg
    b_sum += sumFactor * pb
    a_sum += sumFactor * pa

    stack = stackStart

    for (i = 0; i < radiusPlus1; i++) {
      stack.r = pr
      stack.g = pg
      stack.b = pb
      stack.a = pa
      stack = stack.next
    }

    yp = width

    for (i = 1; i <= radius; i++) {
      yi = (yp + x) << 2

      r_sum += (stack.r = pr = pixels[yi]) * (rbs = radiusPlus1 - i)
      g_sum += (stack.g = pg = pixels[yi + 1]) * rbs
      b_sum += (stack.b = pb = pixels[yi + 2]) * rbs
      a_sum += (stack.a = pa = pixels[yi + 3]) * rbs

      r_in_sum += pr
      g_in_sum += pg
      b_in_sum += pb
      a_in_sum += pa

      stack = stack.next

      if (i < heightMinus1) {
        yp += width
      }
    }

    yi = x
    stackIn = stackStart
    stackOut = stackEnd
    for (y = 0; y < height; y++) {
      p = yi << 2
      pixels[p] = (r_sum * mul_sum) >> shg_sum
      pixels[p + 1] = (g_sum * mul_sum) >> shg_sum
      pixels[p + 2] = (b_sum * mul_sum) >> shg_sum
      pixels[p + 3] = (a_sum * mul_sum) >> shg_sum

      r_sum -= r_out_sum
      g_sum -= g_out_sum
      b_sum -= b_out_sum
      a_sum -= a_out_sum

      r_out_sum -= stackIn.r
      g_out_sum -= stackIn.g
      b_out_sum -= stackIn.b
      a_out_sum -= stackIn.a

      p =
        (x +
          ((p = y + radiusPlus1) < heightMinus1 ? p : heightMinus1) * width) <<
        2

      r_sum += r_in_sum += stackIn.r = pixels[p]
      g_sum += g_in_sum += stackIn.g = pixels[p + 1]
      b_sum += b_in_sum += stackIn.b = pixels[p + 2]
      a_sum += a_in_sum += stackIn.a = pixels[p + 3]

      stackIn = stackIn.next

      r_out_sum += pr = stackOut.r
      g_out_sum += pg = stackOut.g
      b_out_sum += pb = stackOut.b
      a_out_sum += pa = stackOut.a

      r_in_sum -= pr
      g_in_sum -= pg
      b_in_sum -= pb
      a_in_sum -= pa

      stackOut = stackOut.next

      yi += width
    }
  }

  unpremultiplyAlpha(imageData)

  context.putImageData(imageData, top_x, top_y)
}

function stackBlurCanvasRGB (id, top_x, top_y, width, height, radius) {
  if (isNaN(radius) || radius < 1) return
  radius |= 0

  var canvas = document.getElementById(id)
  var context = canvas.getContext('2d')
  var imageData

  try {
    try {
      imageData = context.getImageData(top_x, top_y, width, height)
    } catch (e) {
      // NOTE: this part is supposedly only needed if you want to work with local files
      // so it might be okay to remove the whole try/catch block and just use
      // imageData = context.getImageData( top_x, top_y, width, height );
      try {
        netscape.security.PrivilegeManager.enablePrivilege(
          'UniversalBrowserRead'
        )
        imageData = context.getImageData(top_x, top_y, width, height)
      } catch (e) {
        alert('Cannot access local image')
        throw new Error('unable to access local image data: ' + e)
      }
    }
  } catch (e) {
    alert('Cannot access image')
    throw new Error('unable to access image data: ' + e)
  }

  var pixels = imageData.data

  var x,
    y,
    i,
    p,
    yp,
    yi,
    yw,
    r_sum,
    g_sum,
    b_sum,
    r_out_sum,
    g_out_sum,
    b_out_sum,
    r_in_sum,
    g_in_sum,
    b_in_sum,
    pr,
    pg,
    pb,
    rbs

  var div = radius + radius + 1
  var w4 = width << 2
  var widthMinus1 = width - 1
  var heightMinus1 = height - 1
  var radiusPlus1 = radius + 1
  var sumFactor = radiusPlus1 * (radiusPlus1 + 1) / 2

  var stackStart = new BlurStack()
  var stack = stackStart
  for (i = 1; i < div; i++) {
    stack = stack.next = new BlurStack()
    if (i == radiusPlus1) var stackEnd = stack
  }
  stack.next = stackStart
  var stackIn = null
  var stackOut = null

  yw = yi = 0

  var mul_sum = mul_table[radius]
  var shg_sum = shg_table[radius]

  for (y = 0; y < height; y++) {
    r_in_sum = g_in_sum = b_in_sum = r_sum = g_sum = b_sum = 0

    r_out_sum = radiusPlus1 * (pr = pixels[yi])
    g_out_sum = radiusPlus1 * (pg = pixels[yi + 1])
    b_out_sum = radiusPlus1 * (pb = pixels[yi + 2])

    r_sum += sumFactor * pr
    g_sum += sumFactor * pg
    b_sum += sumFactor * pb

    stack = stackStart

    for (i = 0; i < radiusPlus1; i++) {
      stack.r = pr
      stack.g = pg
      stack.b = pb
      stack = stack.next
    }

    for (i = 1; i < radiusPlus1; i++) {
      p = yi + ((widthMinus1 < i ? widthMinus1 : i) << 2)
      r_sum += (stack.r = pr = pixels[p]) * (rbs = radiusPlus1 - i)
      g_sum += (stack.g = pg = pixels[p + 1]) * rbs
      b_sum += (stack.b = pb = pixels[p + 2]) * rbs

      r_in_sum += pr
      g_in_sum += pg
      b_in_sum += pb

      stack = stack.next
    }

    stackIn = stackStart
    stackOut = stackEnd
    for (x = 0; x < width; x++) {
      pixels[yi] = (r_sum * mul_sum) >> shg_sum
      pixels[yi + 1] = (g_sum * mul_sum) >> shg_sum
      pixels[yi + 2] = (b_sum * mul_sum) >> shg_sum

      r_sum -= r_out_sum
      g_sum -= g_out_sum
      b_sum -= b_out_sum

      r_out_sum -= stackIn.r
      g_out_sum -= stackIn.g
      b_out_sum -= stackIn.b

      p = (yw + ((p = x + radius + 1) < widthMinus1 ? p : widthMinus1)) << 2

      r_in_sum += stackIn.r = pixels[p]
      g_in_sum += stackIn.g = pixels[p + 1]
      b_in_sum += stackIn.b = pixels[p + 2]

      r_sum += r_in_sum
      g_sum += g_in_sum
      b_sum += b_in_sum

      stackIn = stackIn.next

      r_out_sum += pr = stackOut.r
      g_out_sum += pg = stackOut.g
      b_out_sum += pb = stackOut.b

      r_in_sum -= pr
      g_in_sum -= pg
      b_in_sum -= pb

      stackOut = stackOut.next

      yi += 4
    }
    yw += width
  }

  for (x = 0; x < width; x++) {
    g_in_sum = b_in_sum = r_in_sum = g_sum = b_sum = r_sum = 0

    yi = x << 2
    r_out_sum = radiusPlus1 * (pr = pixels[yi])
    g_out_sum = radiusPlus1 * (pg = pixels[yi + 1])
    b_out_sum = radiusPlus1 * (pb = pixels[yi + 2])

    r_sum += sumFactor * pr
    g_sum += sumFactor * pg
    b_sum += sumFactor * pb

    stack = stackStart

    for (i = 0; i < radiusPlus1; i++) {
      stack.r = pr
      stack.g = pg
      stack.b = pb
      stack = stack.next
    }

    yp = width

    for (i = 1; i <= radius; i++) {
      yi = (yp + x) << 2

      r_sum += (stack.r = pr = pixels[yi]) * (rbs = radiusPlus1 - i)
      g_sum += (stack.g = pg = pixels[yi + 1]) * rbs
      b_sum += (stack.b = pb = pixels[yi + 2]) * rbs

      r_in_sum += pr
      g_in_sum += pg
      b_in_sum += pb

      stack = stack.next

      if (i < heightMinus1) {
        yp += width
      }
    }

    yi = x
    stackIn = stackStart
    stackOut = stackEnd
    for (y = 0; y < height; y++) {
      p = yi << 2
      pixels[p] = (r_sum * mul_sum) >> shg_sum
      pixels[p + 1] = (g_sum * mul_sum) >> shg_sum
      pixels[p + 2] = (b_sum * mul_sum) >> shg_sum

      r_sum -= r_out_sum
      g_sum -= g_out_sum
      b_sum -= b_out_sum

      r_out_sum -= stackIn.r
      g_out_sum -= stackIn.g
      b_out_sum -= stackIn.b

      p =
        (x +
          ((p = y + radiusPlus1) < heightMinus1 ? p : heightMinus1) * width) <<
        2

      r_sum += r_in_sum += stackIn.r = pixels[p]
      g_sum += g_in_sum += stackIn.g = pixels[p + 1]
      b_sum += b_in_sum += stackIn.b = pixels[p + 2]

      stackIn = stackIn.next

      r_out_sum += pr = stackOut.r
      g_out_sum += pg = stackOut.g
      b_out_sum += pb = stackOut.b

      r_in_sum -= pr
      g_in_sum -= pg
      b_in_sum -= pb

      stackOut = stackOut.next

      yi += width
    }
  }

  context.putImageData(imageData, top_x, top_y)
}

function BlurStack () {
  this.r = 0
  this.g = 0
  this.b = 0
  this.a = 0
  this.next = null
}
